FlAsH-ID: A short peptide tag for live cell photoproximity labeling

Furthermore, we show that FlAsH-ID can be used to probe dynamic chnages in protein movement in response to immune stimuli, identifying several RNA-binding protiens that are trafficked to the nucleus following poly(I:C) treatment. Finally we demonstrate FlAsH-ID can be used for proximity proteomics in primary CD8+ T cells by focusing on the transcription factor RUNX3. RUNX3-tetracysteine, but not RUNX3-TurboID, recaptiulated the function of wildtype RUNX3 and rescued the phenotype of Runx3-deficeint CD8+ T cells in response to viral infection in vivo.

In primary CD8+ T cells, FlAsH-ID identified RUNX3 in proximity to the nucleosome remodeler ARID1A and we show that both factors act concertedly during initial naive CD8+ T cell activation to drive chromatin accessibility in cis-regulatory regions that induce differentiation of effector and long-lived memory CD8+ T cells. Our results suggest this technique will expand the field of proximity labeling to small, functionally sensitive proteins in primary cells without perturbing their function.